1. Cloud Property Retrievals over the Arctic from the NASA A-Train Satellites Aqua, CloudSat and CALIPSO
Douglas Spangenberg1, Patrick Minnis2,
Michele L. Nordeen1, Sunny Sun-Mack1
and Q. Z. Trepte1
1- Science Systems and Applications, Inc, Hampton, VA, USA
2- NASA Langley Research Center, Hampton, VA, USA

2. NASA A-Train Constellation
CALIPSO
(Lidar)
CloudSat
(Radar)
Aqua
(MODIS)
15 sec
0.5-2 min

3. North Pole A-Train Orbit Tracks: April 19, 2008

4. A-Train Satellites • Passive MODIS sensor Aqua:
•1km res pixels sub-sampled to 2 km for cloud property retrievals
• Channels used for cloud detection, cloud property retrievals (NASA CERES algorithm): 0.65, 2.1, 1.38, 3.7, 6.7, 7.3, 8.5,11,12,13.3 mm
- Original Algo, Cloud Detection/Phase, Cloud-Top Altitude
• Cloud Properties: Z,T, Phase, t, LWP, IWP, Particle Size
CloudSat:
• 94 GHz Cloud Profiling Radar
• 2.5x1.4 km horizontal res; 240 m vertical res
• Cloud properties: t, LWC/LWP, IWC/IWP, Particle Size
CALIPSO:
• Cloud-Aerosol lidar with 532, 1064 nm channels
• km horizontal res; 30, 60 m vertical res
• Cloud properties: N layers, T, Z, Phase, t, IWP
• Lidar attenuates after t=5; often can’t see to cloud base

5. A-Train Cloud Analysis, 22:25 UTC Apr 19, 2008
Aqua 11mm BT
A-Train
R: 0.65 mm
G: mm
B: 11 mm
Aqua RGB
Aqua Cloud Phase
Aqua Optical Depth

6. A-Train Cloud Analysis: 22:25 UTC Apr 19, 2008
CALIPSO VFM
A-Train
Aqua Cloud Phase
CALIPSO Phase

7. A-Train Cloud Analysis: 22:25 UTC Apr 19, 2008
Aqua 11mm BT
A-Train
CloudSat Ice Re
CloudSat Reflectivity
CloudSat IWC

8. A-Train Cloud Analysis: 22:25 UTC Apr 19, 2008
CloudSat Liq Re
Aqua Liquid Re
A-Train
CloudSat LWC

9. Aqua-MODIS Validation
• Compare CERES Aqua-MODIS cloud property retrievals to CloudSat/CALIPSO retrievals (passive vs active sensor retrievals)
• Results from April 2008 afternoon/daytime overpasses, 22-23:30 GMT
• ARM/ISDAC field experiment flight days
• Region: 60-80N; W
• Nearest 4 Aqua-MODIS pixels along CloudSat/CALIPSO track used
• CALIPSO & CloudSat data points matched to within 4 km, 4 min

10. Aqua-MODIS Validation
CALIPSO Scene Types Sampled:
Cloud Amount & Phase Matching between CALIPSO & Aqua:
• Results valid for CALIPSO upper-most cloud layer

11. Aqua-MODIS Validation
Cloud Top Height, CALIPSO vs Aqua:
CALIPSO mean: 5.24 km
Aqua mean: 4.39 km
Aqua bias: km

12. Aqua-MODIS Validation
Ice Crystal Effective Diameter, CloudSat vs Aqua:

13. New Aqua-MODIS Multilayer Cloud Property Retrievals
April , 22:20 GMT
SL/UL Ztop
Low-Level Ztop
Aqua Optical Depth
• Uses 13.3 mm channel/CO2 slicing to detect multilayer clouds
• t, Re, T, Z, e for low (liquid) layer
• Can improve ice cloud detection by adjusting highest cloud top upward

14. Summary & Future Work
• CALIPSO, CloudSat provide data for validating Aqua-MODIS cloud property retrievals on a continuous basis over remote Arctic/Antarctic.
• A-Train data can be compared with cloud model data & retrievals from passive sensors on geo satellites (validation studies).
• CALIPSO reported combinations of ice and liquid phase in low level Arctic clouds rather than reporting mixed phase.
• Problem in CloudSat data for clouds below ~1km, to hopefully be resolved.
• In-situ data obtained during field experiments will provide valuable data for validating CALIPSO/CloudSat retrievals (ISDAC/AK-Apr 2008).

15. Summary & Future Work
• Comparisons between Aqua passive sensor retrievals and active sensor retrievals of CALIPSO show good agreement for cloud amount, phase, height.
• Comparisons between Aqua and CloudSat t, particle size, LWP/IWP showed larger discrepancy which needs to be resolved
- Account for differences inherent in retrievals methods
- Improve Aqua-MODIS retrieval techniques for polar clouds
• Multilayer Aqua-MODIS cloud algorithm should be able to provide improved retrievals for high ice clouds and low mixed/liq clouds.
• Web Pages for Information/Data Access:
- CALIPSO:
- CloudSat: